Ammunition



Patented Mar. 12, 1940 AMMUNITION No Drawing. Application September 3,1936, Serial No. 99,310

2 Claims.

This invention relates to the manufacture of shot, and contemplates shotmade by a metal hitherto unused for this purpose as well as a method forthe production of shot from this 5' metal.

Commercial shot as used in shot gun shells or cartridges consist chieflyof lead, hardening agents such as antimony and/or arsenic being presentin small but controlled amounts. Such shot are manufactured by preparinga melt of the lead,

running the molten metal into a sieve or dropping pan, upon theunderside of which droplets of molten lead are formed to a sizedetermined by the size of the apertures in the pan and the temperatureand composition of the metal, and,

upon reaching the size so determined, are detached from the pan by theirown weight and fall through the air a distance of the order of 130 feet.During theirfall, they are solidified sufiiciently to withstand impactwith a cushioning body of water placed at the bottom of the droppingtower, from which they are removed as fully formed shot substantiallyready for use. The number of spherical shot pellets required in theammunition industry is such as to substantially preclude manufacture bythe conventional metal working methods of casting, grinding or rolling.

Lead shot are subject to certain disadvantages. They are poisonous togame birds, when taken internally; the poisoning of ducks in the marshesover which there has been a great dealof shooting having become aproblem of such magnitude as to receive the attention of the UnitedStates Biological Survey. Moreover, the density of lead 85 is so greatthat for some uses lead shot are undesirably heavy. With a given amountof energy lighter pellets may be given a substantially higher initialvelocity, which velocityis sufficiently sustained to accomplish thedesired purpose. Air

rifle shot, for example, should be projected with considerable velocity,but an excess of residual energy after a flight of medium range isundesirable. The need for non-poisonous and lighter shot has long beenrecognized, but prior to the present invention, it has been deemedimpracticable to drop shot of the lighter, harder, nonpoisonous metals.Lead offers a unique combination of low melting point and low heat offusion, which permits the dropping of lead shot in the manner heretoforedescribed. The melting points of other metals are usually so high thatit is impracticable to secure a melt of sufficient fluidity to bedropped through apertures of small size, their surface tensioncharacteristics are 5 not such as to form spherical shot on dropping,

or their heat of fusion and/or heat generated by surface oxidation is sogreat that they do not solidify upon dropping any practicable distance.

The present invention comprises the discovery that by proper treatmentand control shot may 5 be dropped which consists almost entirely ofzinc. Pure zinc has a melting point of about 788 F., and becomessufiiciently fluid to run through a dropping pan at a temperature ofabout 1150 F. At this high temperature, however, it is diffi- 10 cult toprevent rapid oxidation of the melt in the kettle, the metal tends tostream through the apertures in the dropping pan instead of formingspherical globules, and such separate particles as are formed do notalways solidify upon dropping down the tower. While it is possible todrop shot of substantially pure zinc, they are accompanied by an amountof scrap metal which tends to be excessive.

The process and the yield are both greatly improved by the addition tothe zinc of a suitable amount of an alloying substance such as sodium ora commercial sodium-zinc alloy. The metal then resists oxidation, bothin the melting kettle and dropping pan and while falling down the tower.It likewise acquires such a surface tension as to form spherical pelletsand becomes fluid at much lower temperatures. The droplets, due to theimproved surface tension, resistance to oxidation, and lower temperatureat which they leave the pan, are solidified in the air drop of aboutfeet, instead of remaining in such a liquid or plastic state that theyare broken up upon impact with the water.

The sodium content may vary from about .1 of 1% up to or evensubstantially beyond a content corresponding to the composition of theKnown zinc-sodium compound of the probable formula NaZmz. This is about2%. If sodium in excess of the compound composition quantity is present,the excess, being free, as distinguished from being in combination withthe zinc, reacts with water, and in water the shot disintegrate. Forsome purposes this characteristic is advantageous. The loss of waterfowl by lead poisoning comes about through the swallowing by the waterfowl of poisonous lead shot which have accumulated as a result ofextensive shooting over the shallow water feeding grounds. By using aneX- cess of sodium in zinc shot, the shot, although non-poisonous, aremade to actually disintegrate so that no accumulation of shot ispossible. If the characteristic of disintegrating in water is notdesired, as for shooting at flying targets or for air rifle shot, thesodium content should be below the compound composition quantity.Generally stated, increasing the sodium content lowers the droppingtemperature. A low dropping temperature is desirable, particularly in astandard dropping tower of a height of about 130 feet, since from thelower temperature there is less heat to be lost before the shot dropletssolidify. However, other factors such as specific heat and heat offusion have a very important bearing on solidification and sphericity.If the metal is readily susceptible to oxidation, the heat generated atthe surface of the droplets while falling down the tower maysubstantially exceed the heat of fusion. Likewise, surface oxidation ofthe droplet before it is detached from the dropping pan may prevent theformation of spheres, causing the droplets to assume an elongatedinstead of a spherical shape. It is believed that the sodium or oxidesof sodium not only act as flux, but likewise prevents surface oxidationof the Zinc and supplies such a surface tension as to materially assistin the forming of spherical, rather than elongated, droplets. l sodiumcontent of the order of is preferred. Shot according to this inventionhave been dropped successfully with temperatures as high as 1100 F. andas low as 810 F.

It has been found that for a given size of shot the dropping panapertures for zinc or a zincsodium alloy should be somewhat smaller thanfor the same size of lead shot. "Under some circumstances it isdesirable that during dropping the dropping pan be subjected to a seriesof rapid light blows. This tends to prevent clogging of the aperturesbut likewise tends to increase the of the droplets formed beneath theapertures of a given size. Cooling and solidification in th tower may befacilitated by providing an upward draft of air of greater or lessintensity or by introducing into the tower a fine spray of water.Similar results can be secured by increasing the height of the tower. Itappears to be essential that the droplets be in a substantially solidcondition before impact with the water, the water acting chiefly as acushioning medium to prevent distortion of the shot by direct impactwith a solid surface.

The shot thus made may be plated if desired with one or more metals. Forexample, a plating of copper applied directly or a plating of nickelupon the shot and a surfacing of copper on the nickel. Such plating maybe accomplished by any of the known plating methods, including contactplating by dropping the shot through the tower into a plating solution,rather than into water.

Zinc or zinc-sodium shot as heretofore described are used in the samemanner as other shot, either for individual iring in air guns or forloading into shot shells for general or particular uses.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that I do not limit myself to the specific embodimentsthereof except as defined in the appended claims.

l/Vhat is claimed is:

"he process of making substantially spherical shot 5 'table for use inthe manufacture of triciges, which comprises alloying than 2% of sodium,separating the molten alloy into globules at the top of a shot tower,and dropping the globules a distance sufficient to enable them tosolidify into substantially spherical shot.

2. In the manufacture of substantially spherical shot suitable for usein shotgun cartridges and consisting substantially of zinc, the methodof controlling the fo ation of spherical pellets and preventingexcessive oxidation while droppin such pellets through a distancesufiicient to substantially solidify them, which comprises a1- loyingwith the zinc not more than 2% of sodium, separating the alloy intoglobules at the top of a shot tower, and dropping said globules throughsaid tower into an impact cushioning medium.

JOHN R. EALDER. THOM -S BAILEY CURRAN.

